ftell(3p)

Usage

#include <stdio.h>

long ftell(FILE *stream); off_t ftello(FILE *stream);

Prolog

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

Overview

The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of POSIX.1‐2017 defers to the ISO C standard.

The ftell() function shall obtain the current value of the file-position indicator for the stream pointed to by stream.

The ftell() function shall not change the setting of errno if successful.

The ftello() function shall be equivalent to ftell(), except that the return value is of type off_t and the ftello() function may change the setting of errno if successful.

Return value

Upon successful completion, ftell() and ftello() shall return the current value of the file-position indicator for the stream measured in bytes from the beginning of the file.

Otherwise, ftell() and ftello() shall return -1, and set errno to indicate the error.

Errors

The ftell() and ftello() functions shall fail if:

EBADF: The file descriptor underlying stream is not an open file descriptor.

EOVERFLOW: For ftell(), the current file offset cannot be represented correctly in an object of type long.

EOVERFLOW: For ftello(), the current file offset cannot be represented correctly in an object of type off_t.

ESPIPE: The file descriptor underlying stream is associated with a pipe, FIFO, or socket.

The following sections are informative.

Examples

None.

Application usage

None.

Rationale

None.

Future directions

None.